The present invention relates to a personal ornament wherein a basis material composed of a copper alloy or zinc is covered with, as an outermost layer, a colored coating of, for example, titanium nitride formed by dry-plating such as the ion plating process, and further relates to a process for producing the personal ornament.
Personal ornaments wherein a basis material composed of a copper alloy or zinc is covered with, as an outermost layer, a colored coating of, for example, titanium nitride formed by the ion plating process are known. For example, Japanese Patent Publication No. 6(1994)-2935 whose applicant is identical with that of the present application discloses a personal ornament with a colored surface, comprising a personal ornament basis material composed of a copper alloy, a 1 to 10 xcexcm thick nickel layer formed as an undercoat layer on a surface thereof by electroplating, a 0.5 to 5 xcexcm thick palladium or palladium alloy (for example, palladium/nickel) layer formed on the nickel layer by electroplating and a colored coating layer of, for example, titanium nitride formed on the palladium or palladium alloy layer by the ion plating process. This personal ornament, because it is not needed to thicken the nickel layer, is free from pattern unsharpness and sagging attributed to thick plating, exhibits an appearance of superior quality and is excellent in corrosion resistance.
However, this personal ornament, although involving no practical problem, poses a cost problem due to the inclusion of the palladium or palladium/nickel layer. The price of palladium (Pd) as a constituent of the layer is recently very high, thereby extremely increasing the production cost of the personal ornament. For example, the price of palladium was about 500 yen/g in 1997, but currently (1998) it is as high as 1400 yen/g. Moreover, ammonia gas emitted at the electroplating conducted for the formation of the palladium/nickel layer is likely to be detrimental to other cyanide using platings (14 or 18 karat Au/Ag plating). Further, the palladium/nickel layer tends to occlude hydrogen, so that cracking of the palladium/nickel layer is likely to occur resulting unfavorable lowering of the adhesion to the colored coating layer and lowering of the durability (corrosion resistance) of the palladium/nickel layer.
Further, Japanese Patent Laid-open Publication No. 4(1992)-304386 whose applicant is identical with that of the present application discloses a basis material composed of a material of low melting point such as brass, german silver (nickel silver or argentan) or zinc die cast, a nickel layer formed as an undercoat layer on a surface of the basis material by wet-plating, a nickel/phosphorus alloy layer formed directly on the nickel layer by electroplating and a dry plating layer (colored coating layer) formed on the nickel/phosphorus alloy layer by dry-plating. With respect to this metal member, the amount of ammonia gas emitted at the electroplating conducted for the formation of the nickel/phosphorus alloy layer is so small that the ammonia gas is substantially free from adversely affecting other platings (ion plating process (dry-plating)). Also, the nickel/phosphorus alloy layer substantially does not occlude hydrogen and is free from cracking, so that there is no danger of lowering of the adhesion to the dry plating layer (colored coating layer) and lowering of the durability of the nickel/phosphorus alloy layer. In particular, the metal member described in Example 1 of Japanese Patent Laid-open Publication No. 4(1992)-304386, because of the formation of a nickel/phosphorus alloy layer having a phosphorus content of about 10%, is excellent in durability and poses no practical problem at all. Although not described in the above Japanese Patent Laid-open Publication No. 4(1992)-304386, the nickel/phosphorus alloy layer of Example 1 thereof is formed by electroplating at a current density (Dk) of 5 A/dm2 at 55xc2x0 C. in a pH 4.0 acid plating solution which contains nickel sulfate in an amount, in terms of nickel atom, of 50 g/lit., nickel chloride in an amount, in terms of nickel atom, of 15 g/lit. and sodium hypophosphite in an amount, in terms of phosphorus atom, of 35 g/lit. Electroplating in this plating solution under the above plating conditions for a prolonged current passage time, however, does not lead to formation of an amorphous nickel/phosphorus alloy layer having a phosphorus content of 11% by weight or more.
The inventors have conducted extensive and intensive studies with a view toward obtaining a personal ornament of high grade having a corrosion resistance greater than those of personal ornaments and metal members disclosed in the above publications without the use of expensive palladium. As a result, it has been found that the following personal ornament produced as described below (1) or (2) includes an amorphous nickel/phosphorus alloy plating layer whose phosphorus content is in the range of 11 to 16% by weight and has a corrosion resistance greater than those of personal ornaments and metal members disclosed in the above publications. The present invention has been completed on the basis of this finding.
Personal ornament (1): This is produced by the following process. First, a nickel plating layer of 1 to 5 xcexcm thickness is formed by electroplating on a surface of a basis material for personal ornament composed of a copper alloy or zinc. Alternatively, a copper plating layer of 10 to 15 xcexcm thickness is formed on the basis material by electroplating, and a surface of the copper plating layer is covered by electroplating with a nickel plating layer of 1 to 10 xcexcm thickness. Subsequently, an amorphous nickel/phosphorus alloy coating layer of 3 to 10 xcexcm thickness (phosphorus content: 11 to 16% by weight) is formed on a surface of the nickel plating layer by electroplating at a current density (Dk) of 1 to 3 A/dm2, at 50 to 60xc2x0 C., in an acid plating solution of pH 3.0 to 3.5 which contains nickel sulfate in an amount, in terms of nickel atom, of 15 to 70 g/lit., sodium hypophosphite in an amount, in terms of phosphorus atom, of 10 to 50 g/lit., an electric conductive salt (ammonium chloride) in an amount of 50 to 90 g/lit., a pH buffer in an amount of 20 to 50 g/lit. and a completing agent in an amount of 5 to 30 g/lit. Finally, a 0.1 to 2 xcexcm thick colored coating layer is formed by dry-plating on a surface of the amorphous nickel/phosphorus alloy plating layer.
Personal ornament (2): This is produced by the following process. First, a nickel plating layer of 1 to 10 xcexcm thickness is formed by electroplating on a surface of a basis material for personal ornament composed of a copper alloy or zinc. Alternatively, a copper plating layer of 10 to 15 xcexcm thickness is formed on the basis material by electroplating, and thereafter a surface of the copper plating layer is covered by electroplating with a nickel plating layer of 1 to 10 xcexcm thickness. Subsequently, an amorphous nickel/phosphorus alloy coating layer layer of 3 to 10 xcexcm thickness (phosphorus content: 11 to 16% by weight) is formed on a surface of the nickel plating (coating) by electroless plating in a plating solution which contains a nickel salt such as nickel sulfate in an amount, in terms of nickel atom, of 1 to 15 g/lit., sodium hypophosphite (reducing agent) in an amount, in terms of phosphorus atom, of 5 to 30 g/lit., a complexing agent, a buffer and a pH regulator, at 85 to 95xc2x0 C. and pH of 3.0 to 4.5. Alternatively, the amorphous nickel/phosphorus alloy coating layer of 3 to 10 xcexcm thickness (phosphorus content: 11 to 16% by weight) is formed by first electroplating by passing current at a density (Dk) of 0.5 to 1.0 A/dm2 for a period of 5 to 30 sec through the above plating solution whose pH is in the range of 3.0 to 4.5 and whose temperature is in the range of 50 to 95xc2x0 C. and thereafter electroless plating in the plating solution whose pH is in the range of 3.0 to 4.5 and whose temperature is in the range of 85 to 95xc2x0 C. Finally, a colored coating layer of 0.1 to 2 xcexcm thickness is formed by dry-plating on a surface of the amorphous nickel/phosphorus alloy plating layer.
Accordingly, an object of the present invention is to provide a cheap personal ornament having a corrosion resistance greater than those of personal ornaments and metal members disclosed in the above publications without the use of expensive palladium and to provide a process for producing the same.
According to one essential aspect o f the present invention, there is provided a personal ornament having its surface covered with a colored coating, the colored coating formed by dry-plating, which personal ornament comprises:
a basis material for personal ornament, composed of a copper alloy or zinc,
a nickel plating (coating) layer on a surface of the basis material, or a nickel plating layer on a surface of a copper plating layer on a surface of the basis material,
an amorphous nickel/phosphorus alloy plating layer on a surface of the nickel plating layer, and
at least one colored coating layer on a surface of the amorphous nickel/phosphorus alloy plating layer, the colored coating layer formed by dry-plating,
the amorphous nickel/phosphorus alloy plating layer having a phosphorus content of 11 to 16% by weight.
As one form (the first form) of the personal ornament covered with a colored coating according to the present invention, there is provided a personal ornament having its surface covered with a colored coating, the colored coating formed by dry-plating, which personal ornament comprises:
a basis material for personal ornament, composed of a copper alloy or zinc,
a nickel plating layer on a surface of the basis material, or a nickel plating layer superimposed on a surface of a copper plating layer on a surface of the basis material,
an amorphous nickel/phosphorus alloy plating layer on a surface of the nickel plating layer, the amorphous nickel/phosphorus alloy plating layer formed in a plating solution which contains nickel sulfate in an amount, in terms of nickel atom, of 15 to 70 g/lit., sodium hypophosphite in an amount, in terms of phosphorus atom, of 10 to 50 g/lit., an electric conductive salt in an amount of 50 to 90 g/lit., a pH buffer in an amount of 20 to 50 g/lit. and a complexing agent in an amount of 5 to 30 g/lit., and
at least one colored coating layer on a surface of the amorphous nickel/phosphorus alloy plating layer, the colored coating layer formed by dry-plating,
the amorphous nickel/phosphorus alloy plating layer having a phosphorus content of 11 to 16% by weight.
The above amorphous nickel/phosphorus alloy plating layer may be one obtained by electroplating at a current density (Dk) of 1 to 3 A/dm2 and temperature of in the range of 50 to 60xc2x0 C. in the above plating solution whose pH is in the range of 3.0 to 3.5.
The above complexing agent may be at least one member selected from the group consisting of citric acid, tartaric acid, malonic acid, malic acid, glycine, gluconic acid and salts thereof.
As another form (the second form) of the personal ornament covered with a colored coating according to the present invention, there is provided a personal ornament having its surface covered with a colored coating, the colored coating formed by dry-plating, which personal ornament comprises:
a basis material for personal ornament, composed of a copper alloy or zinc,
a nickel plating layer on a surface of the basis material, or a nickel plating layer on a surface of a copper plating layer on a surface of the basis material,
an amorphous nickel/phosphorus alloy plating layer on a surface of the nickel plating layer, the amorphous nickel/phosphorus alloy plating layer formed by electroless plating in a plating solution which contains a nickel salt in an amount, in terms of nickel atom, of 1 to 15 g/lit., sodium hypophosphite (reducing agent) in an amount, in terms of phosphorus atom, of 5 to 30 g/lit., a complexing agent, a buffer and a pH regulator, or by first electroplating in the plating solution and thereafter electroless plating in the same plating solution, and
at least one colored coating layer on a surface of the amorphous nickel/phosphorus alloy plating layer, the colored coating layer formed by dry-plating,
the amorphous nickel/phosphorus alloy plating layer having a phosphorus content of 11 to 16% by weight.
The plating solution for use in the electroless plating or in the electroplating followed by the electroless plating may have a pH of 3.0 to 4.5 and a temperature of 50 to 95xc2x0 C.
The above colored coating layer may be at least one layer selected from the group consisting of a metal coating layer, a coating layer of metal nitride, a coating layer of metal carbide, a coating layer of metal oxide, a coating layer of metal carbonitride, a coating layer of metal oxynitride, a coating layer of metal oxycarbide and a coating layer of metal oxycarbonitride.
In the personal ornament covered with a colored coating according to the present invention, the nickel plating layer may have a thickness of 1 to 10 xcexcm, the amorphous nickel/phosphorus alloy plating layer may have a thickness of 3 to 10 xcexcm, and the colored coating layer may have a thickness (total thickness in the event of a plurality of colored coating layers) of 0.1 to 2 xcexcm.
For obtaining the first form of personal ornament covered with a colored coating according to the present invention, there is provided a process for producing a personal ornament having its surface covered with a colored coating , the colored coating formed by dry-plating, which process comprises the steps of:
electroplating a surface of a basis material for personal ornament composed of a copper alloy or zinc to thereby form a nickel plating layer on the surface, or first electroplating a surface of the basis material to thereby form a copper plating layer on the surface and thereafter electroplating a surface of the copper plating layer to thereby form a nickel plating layer on the surface of the copper plating layer,
electroplating a surface of the nickel plating layer in a plating solution which contains nickel sulfate in an amount, in terms of nickel atom, of 15 to 70 g/lit., sodium hypophosphite in an amount, in terms of phosphorus atom, of 10 to 50 g/lit., an electric conductive salt in an amount of 50 to 90 g/lit., a pH buffer in an amount of 20 to 50 g/lit. and a completing agent in an amount of 5 to 30 g/lit. to thereby form on the surface of the nickel plating layer an amorphous nickel/phosphorus alloy plating layer having a phosphorus content of 11 to 16% by weight, and
subjecting a surface of the amorphous nickel/phosphorus alloy plating layer to dry-plating so that at least one colored coating layer is formed on the surface.
The above formation of the amorphous nickel/phosphorus alloy plating layer may be performed at a current density (Dk) of 1 to 3 A/dm2 in the plating solution whose temperature is in the range of 50 to 60xc2x0 C.
The above complexing agent may be at least one member selected from the group consisting of citric acid, tartaric acid, malonic acid, malic acid, glycine, gluconic acid and salts thereof.
For obtaining the second form of personal ornament covered with a colored coating according to the present invention, there is provided a process for producing a personal ornament having its surface covered with a colored coating formed by dry-plating, which process comprises the steps of:
electroplating a surface of a basis material for personal ornament composed of a copper alloy or zinc to thereby form a nickel plating layer on the surface, or first electroplating a surface of the basis material to thereby form a copper plating layer on the surface and thereafter electroplating a surface of the copper plating layer to thereby form a nickel plating layer on the surface of the copper plating layer,
electroless plating a surface of the nickel plating layer in a plating solution which contains a nickel salt in an amount, in terms of nickel atom, of 1 to 15 g/lit., sodium hypophosphite (reducing agent) in an amount, in terms of phosphorus atom, of 5 to 30 g/lit., a completing agent, a buffer and a pH regulator, or first electroplating a surface of the nickel plating layer in the plating solution and thereafter electroless plating the surface in the same plating solution, to thereby form on the surface of the nickel plating layer an amorphous nickel/phosphorus alloy plating layer having a phosphorus content of 11 to 16% by weight, and
subjecting a surface of the amorphous nickel/phosphorus alloy plating layer to dry-plating so that at least one colored coating layer is formed on the surface.
The above amorphous nickel/phosphorus alloy plating layer may be formed by electroless plating in the plating solution whose pH is in the range of 3.0 to 4.5 and temperature is in the range of 85 to 95xc2x0 C. Alternatively, the amorphous nickel/phosphorus alloy plating layer may be formed by first electroplating by passing current at a density (Dk) of 0.5 to 3.0 A/dm2 for a period of 5 to 30 sec through the plating solution whose pH is in the range of 3.0 to 4.5 and temperature is in the range of 50 to 95xc2x0 C. and thereafter electroless plating in the plating solution.
In the personal ornament obtained by the process for producing a personal ornament covered with a colored coating according to the present invention, the phosphorus content of the amorphous nickel/phosphorus alloy coating layer is in the range of 11 to 16% by weight.
The above colored coating layer may be at least one layer selected from the group consisting of a metal coating layer, a coating layer of metal nitride, a coating layer of metal carbide, a coating layer of metal oxide, a coating layer of metal carbonitride, a coating layer of metal oxynitride, a coating layer of metal oxycarbide and a coating layer of metal oxycarbonitride.
In the personal ornament obtained by the process for producing a personal ornament covered with a colored coating according to the present invention, the nickel plating layer may have a thickness of 1 to 10 xcexcm, the amorphous nickel/phosphorus alloy plating layer may have a thickness of 3 to 10 xcexcm, and the colored coating layer may have a thickness (total thickness in the event of a plurality of colored coating layers) of 0.1 to 2 xcexcm.